The present invention relates to devices and methods for administering or delivering substances, including injection devices and methods for making and using them. More particularly, it relates to an injection device for administering an injectable product, in doses, from a product container or ampoule provided with a piston.
In one embodiment, the injection device comprises a generally tubular activating means which can be driven manually, an operating button on which axial movements and rotational movements can be performed, a drive element which is non-rotatably connected to the operating button and follows the movements of the operating button, and a driven member, operably coupled to the drive element, which can be moved in the advancing direction of the piston, wherein when the operating button is moved axially, the drive element can be shifted in the advancing direction of the piston from a resting position to an end position and back again, this movement transferable onto the driven member.
An injection device of the type suitable for the present invention is known from EP 0 581 924 B1 (belonging to the Applicant), the disclosure and teachings of which are incorporated herein by reference. The known injection device serves to inject respectively selectable amounts of a liquid product, which preferably contains a medical or therapeutic active agent, from a product container provided with a piston, in particular from an ampoule. The device comprises a tubular activating means which can be driven manually and which comprises an operating button which can be axially and rotationally moved, a drive element which is non-rotatably connected to the operating button and follows the movements of the operating button, a driven member which is non-rotatable with respect to a casing of the device, and a guiding element for the driven member.
In the known device, a drive element—on which the driven member is movably mounted—can be shifted axially, i.e. in the advancing or dispensing direction of the piston, by a distance predefined by the mechanism, from a resting position to a front end position. The product dosage to be delivered is set by rotating the operating button.
In one embodiment, a rotational grid is provided between non-rotatable and rotatable parts of the known injection device and comprises two discoid locking elements which oppose each other and each comprise a plurality of locking protrusions and a plurality of locking recesses preferably corresponding to or complementing the locking protrusions, and which co-operate with each other.
When the dosage to be injected is set by rotating the operating button, the locking protrusions slide off on the locking recesses, producing a sound which is uniquely dependent on the rotational movement of the operating button. In the device of EP 0 581 924 B1, a clicking sound is produced every time the locking protrusions resile into the locking recesses formed to correspond to them. By counting out on the basis of the sound produced, in particular on the basis of the number of clicking sounds, the patient can set the quantity of the new injection dosage purely aurally, i.e., without looking at the device. Setting the dosage to be injected aurally in this way has proven very advantageous, in particular for patients who have developed impaired vision due to an illness, as is, for example, often the case with diabetes patients.
In the prior art, the rotational grid consists of two disc-shaped locking elements on which serrated locking protrusions or locking recesses, respectively, are arranged at regular intervals in the circumferential direction. The two locking elements are pressed against each other by means of a spring serving as a restoring element, such that the rotational grid and/or operating button can only be rotated in one rotational direction and are blocked in the other rotational direction. This has the disadvantage that a dosage which has been set by rotating the operating button in the first rotational direction can only then be increased further, i.e., by rotating the operating button further in the first direction, but cannot be reduced by rotating the operating button back in the opposite rotational direction. Thus, if the patient has inadvertently selected too large a dosage, for instance because he has incorrectly counted the number of clicking sounds, then the incorrectly selected dosage must first be delivered by advancing the driven member to the front end position. The driven member must then be moved back to the resting position before a new dosage can be set. This procedure is tedious, fraught with error and unnecessarily wastes a lot of product.